Schottky diodes with Au/ZnO nanorod (NR)/n-SiC configurations have been fabricated and their interface traps and electrical properties have been investigated by current-voltage (I-V), capacitance-voltage (C-V), capacitance-frequency (C-f), and conductance-frequency (Gp/ω-ω) measurements. Detailed and systematic analysis of the frequency-dependent capacitance and conductance measurements was performed to extract the information about the interface trap states. The discrepancy between the high barrier height values obtained from the I-V and the C-V measurements was also analyzed. The higher capacitance at low frequencies was attributed to excess capacitance as a result of interface states in equilibrium in the ZnO that can follow the alternating current signal. The energy of the interface states (Ess) with respect to the valence band at the ZnO NR surface was also calculated. The densities of interface states obtained from the conductance and capacitance methods agreed well with each other and this confirm that the observed capacitance and conductance are caused by the same physical processes, i.e., recombination-generation in the interface states.

/pdf/interface-trap-characterization-and-electrical-properties-of-2x2ip5sjek.pdf

Interface trap characterization and electrical properties of Au-ZnO nanorod Schottky diodes by conductance and capacitance methods

Recent advances in information technology require higher-speed and higher-density memory devices. In the past decade, resistance switching memory has emerged as a powerful alternative to existing charge-storage-based, non-volatile devices. Despite the extensive research, much of the underlying switching/conduction mechanism is still unknown and controversial. The versatile capability of scanning probe microscopy (SPM) has extended the understanding of resistive switching significantly. This review summarizes the recent advances in understanding on the mechanism of resistive switching effects with particular focus on SPM based observations. In addition, the tip-sample interfacial effects and resulting possible artefacts during scanning probe measurements are discussed.

Resistive switching memory: observations with scanning probe microscopy

As a coupling effect of pyroelectric and photoelectric effect, pyro-phototronic effect has demonstrated an excellent tuning role for fast response p–n junction photodetectors (PDs). Here, a comprehensive pyro-phototronic effect is utilized to design and fabricate a self-powered and flexible ultraviolet PD based on the ZnO/Ag Schottky junction. By using the primary pyroelectric effect, the maximal transient photoresponsivity of the self-powered PDs can reach up to 1.25 mA W−1 for 325 nm illumination, which is improved by 1465% relative to that obtained from the steady-state signal. The relative persistent secondary pyroelectric effect weakens the height of Schottky barrier, leading to a reduction of the steady-state photocurrent with an increase in the power density. When the power density is large enough, the steady-state photocurrent turns into a reverse direction. The corresponding tuning mechanisms of the comprehensive pyro-phototronic effect on transient and steady-state photocurrent are revealed based on the bandgap diagrams. The results may help us to further clarify the mechanism of the pyro-phototronic effect on the photocurrent and also provide a potential way to optimize the performance of self-powered PDs.

Comprehensive Pyro-Phototronic Effect Enhanced Ultraviolet Detector with ZnO/Ag Schottky Junction

In this work, bipolar resistive switching characteristics were demonstrated in the Pt/ZnO/Pt structure. Reliability tests show that ac cycling endurance level above 106 can be achieved. However, significant window closure takes place after about 102 dc cycles. Data retention characteristic exhibits no observed degradation after 168 h. Read durability shows stable resistance states after 106 read times. The current transportation in ZnO films is dominated by the hopping conduction and the ohmic conduction in high-resistance and low-resistance states, respectively. Therefore, the electrical parameters of trap energy level, trap spacing, Fermi level, electron mobility, and effective density of states in conduction band in ZnO were identified.

/pdf/reliability-characteristics-and-conduction-mechanisms-in-2icb4yhc89.pdf

Reliability characteristics and conduction mechanisms in resistive switching memory devices using ZnO thin films

Electrochemical properties of redox proteins, which can cause the reversible changes in the resistance according to their redox reactions in solution, are of the fundamental and practical importance in bioelectrochemical applications. These redox properties often depend on the chemical activity of transition metal ions as cofactors within the active sites of proteins. Here, we demonstrate for the first time that the reversible resistance changes in dried protein films based on ferritin nanoparticles can be caused by the externally applied voltage as a result of charge trap/release of FeIII/FeII redox couples. We also show that one ferritin nanoparticle of about 12 nm size can be operated as a nanoscale-memory device, and furthermore the layer-by-layer assembled protein multilayer devices can be extended to bioinspired electronics with adjustable memory performance via molecular level manipulation.

Electrically Bistable Properties of Layer-by-Layer Assembled Multilayers Based on Protein Nanoparticles

Analysis of the electrical characteristics of the Ag/ZnO Schottky barrier diodes on F-doped SnO2 glass substrates by pulsed laser deposition

The Na05Bi05TiO3(NBT) thin films sandwiched between Au electrodes and fluorine-doped tin oxide (FTO) conducting glass were deposited using a sol–gel method Based on electrochemical workstation measurements, reproducible resistance switching characteristics and negative differential resistances were obtained at room temperature A local impedance spectroscopy measurement of Au/NBT was performed to reveal the interface-related electrical characteristics The DC-bias-dependent impedance spectra suggested the occurrence of charge and mass transfer at the interface of the Au/NBT/FTO device It was proposed that the first and the second ionization of oxygen vacancies are responsible for the conduction in the low- and high-resistance states, respectively The experimental results showed high potential for nonvolatile memory applications in NBT thin films

/pdf/study-on-resistance-switching-properties-of-na0-5bi0-1mkpzsl5be.pdf

Study on Resistance Switching Properties of Na0.5Bi0.5TiO3Thin Films Using Impedance Spectroscopy

The electric-pulse-induced resistance switching of the Au–La0.67Ca0.33MnO3(LCMO)-FTO (fluorine-doped tin oxide) heterostructures was studied by electrochemical workstation. A distinct current-voltage characteristic of the device with pronounced reproducible nonlinearity, asymmetry, and hysteresis was observed at room temperature. The current-voltage characteristics suggest a Poole–Frenkel and space-charge-limited current type mechanism controlled by Au/LCMO interface traps. The resistance switching behavior shows obvious multilevel resistance switching. The present results suggest a possible application of Ag-LCMO-FTO system as multilevel memory devices.

Ting Zhang

Papers

Analysis of the electrical characteristics of the Ag/ZnO Schottky barrier diodes on F-doped SnO2 glass substrates by pulsed laser deposition

Study on Resistance Switching Properties of Na0.5Bi0.5TiO3Thin Films Using Impedance Spectroscopy

Resistance switching properties of sol-gel derived La0.67Ca0.33MnO3 thin films on F-doped SnO2 conducting glass